The objective of this project will be to determine the physicochemical and enzymatic properties of the isoenzymic forms of dynein in cilia and flagella. The isoenzymes will be solubilized by differential extraction, and then purified by chromatography on Sepharose 4B and hydroxylapatite. The molecular weights of the isoenzymes will be determined by equilibrium sedimentation, and their shape by electron microscopy after rotary shadowing. The steady state rate of ATP hydrolysis by the different isoenzymes will be determined as a function of pH and ionic strength. These rate profiles will be compared with each others, and with the rate profile of intact flagellar axonemes. The enzymatic effects of the interactions of the isoenzymes with native tubulin, and with other axonemal proteins, will be studied in order to obtain information about the function of the various isoenzymes in the process of flagellar motility. Ogawa, K. and Gibbons, I.R. Dynein 2: A New Adenosine Triphosphatase from Sea Urchin Sperm Flagella. J. Biol. Chem., 251, 5793-5801 (1976). Gibbons, I.R., Structure and Function of Flagellar Microtubules, in Cell Biology, 1976, (B. Brinkley and K. R. Porter, eds.), Rockefeller University Press, New York, in press.